1. Field of the Invention
The present invention relates to a magnetic alloy which has low coercive force, high permeability and high saturation magnetic flux density as well as excellent corrosion resistance and heat resistance and is, therefore, suitable for use as a material for a magnetic head for high density magnetic recording.
2. Description of the Related Art
In recent years, the development of magnetic recording techniques has been remarkable, and recording density has become higher and higher. To increase recording density, it is necessary to provide a magnetic recording medium of higher coercive force. To magnetize a magnetic recording medium of high coercive force, it is necessary to use a magnetic head made of a material having a high saturation magnetic flux density.
As is known, an alloy material, such as "Permalloy", "Sendust" or a Co based amorphous alloy, is conventionally employed as a core material for such a magnetic head. In contrast, the coercive force of magnetic recording media has been increasing more and more, and some magnetic recording media have realized coercive forces not less than 2,000 oersteds (Oe). If the coercive force becomes 2,000 Oe or more, it has been difficult to realize good magnetic recording and reproduction by using a magnetic head using such a conventional alloy material. This is because the saturation magnetic flux density Bs of any of the alloy materials is not greater than 13,000 gausses (=1.3 T).
From the above-described background, a magnetic alloy having a crystallitic structure and a composition represented as Fe-M-C or Fe-M-N (M is Ti, Zr, Hf, V, Nb, Ta, Mo, W or the like) has recently been proposed as a material having a saturation magnetic flux density higher than any of "Permalloy", "Sendust" and the Co based amorphous alloy.
However, to implement good characteristics with the magnetic alloy such as Fe-M-C or Fe-M-N, heat treatment of 450.degree. C. or more is needed, so that it has been impossible to use the magnetic alloy as a material for, in particular, a magnetic head which is formed by a comparatively low temperature process, such as a thin-film magnetic head. Also, during the production of 8 mm VTR heads, heat resistance to a minimum of 550.degree. C. is required to effect glass bonding. However, conventionally, it has not been proposed to provide a material capable of realizing stable magnetic characteristics over such a wide range of heat treatment temperatures.
Also, if a magnetic head made of the aforesaid core material consisting essentially of Fe is employed under high temperature and high humidity conditions, discoloration or rust occurs on the surface of the magnetic head, so that the slide surface of the magnetic head for contact with a magnetic recording medium becomes rough. As a result, spacing loss occurs, and it is impossible to attain satisfactory electromagnetic conversion characteristics.
The relative speeds between magnetic recording media and magnetic heads have been increasing more and more, and there is the possibility that a relative speed in excess of 10 m/sec may appear. If a magnetic recording medium is made to run for a long time at such a high relative speed, the magnetic thin film portion of the core material is abraded. In particular, in the case of an MIG (metal-in-gap) head of the type in, which magnetic thin films are formed on the gap forming faces of a ferrite core, a step difference between the magnetic thin film portion and the ferrite portion occurs due to abrasion, whereby spacing loss is caused. Accordingly, it has been impossible to satisfactorily utilize the electromagnetic characteristics of the MIG head.